The present invention relates to liners such as floatwall panels for use in gas turbine engine combustors, and in particular to floatwall panels with cooling holes for creating a cooling film. Combustors used in commercial gas turbine engines, such as those used in aircraft or power generation, may generate combustion gases at very high temperatures. These temperatures are often high enough to damage the combustor wall unless sufficient cooling is provided. The walls may be cooled in a variety of ways, including impingement cooling, transpiration cooling, convective cooling, or effusion cooling (also called film cooling). The present invention relates to cooling holes used in convective cooling and effusion cooling.
For effective cooling by effusion in a gas turbine engine, many effusion cooling holes are typically created through the wall of the combustion chamber. Often, the wall is made of many floatwall panels, each including effusion cooling holes. The cooling holes may be made by laser ablation or electrical discharge machining These methods of creating cooling holes have disadvantages. For example, electrical discharge machining is typically too slow and expensive to be a feasible option to manufacturers of combustor liners. Laser ablation is a faster, cheaper option, but suffers from line of sight limitations. Such limitations prevent floatwall panels from including effusion cooling holes distributed ideally across the floatwall panel surfaces. This may require overcooling in some areas to achieve the durability required for the floatwall panels. Such overcooling may result in excess consumption of compressed cooling air produced by the engine, with a detrimental effect on the thrust specific fuel consumption of the turbine engine.